I have a feature that I'm integrating into my own app but do think that other different apps in different industries could benefit from it. How should I navigate this? How developed should this tech be (function app, MVP, demo?) before it start reaching out?
To clarify, are you selling a feature or an API integration? Cause it sounds like you're selling an API.
If you are selling this, use the app you have already developed as you MVP and baseline for this API/feature. Show your app both with and without this integration so that the benefits are clear to those looking to onboard.
Because it is an 'extension' you should aim for UX over UI and develop the finer aspects later.
When you say "sell", do you mean license on a SaaS basis or actual transfer of ownership? To your second question, make sure it works perfect in your environment first before you reach out.